On the B+ voltage discussion, let me throw in another element in the interest of some additional perspective, and this applies to all the different amp models. Just as influential as today's higher line voltages when it comes to B+ supply voltage is the bias level being set on the power output tubes and the resulting idle current draw.
Let's take a look at the original Dynaco Mk III schematic from the 1950's or '60s which indicates 117VAC line voltage and a B+ of 480VDC. If we adjust the B+ up 5% or so for present-day line voltage (our line here in the Miami, FL area averages around 123VAC), we should be looking at ~505VDC at the B+ point, as adjusted. (BTW, I've found through numerous measurements at many Variac settings, that the B+ moves in very close linear proportions to changes in line supply voltage at the upper end of the range near normal line voltages) But you say, "Wait a minute -- I'm seeing more like +/-540V at the B+ in my 60W Sunn head! That's a huge difference from 505V -- what's the deal?" Sunn doesn't specify (at least not that I've ever been able to find looking at what seems to be every schematic they ever published) the output stage idle current draw specification. (They do show -55V at the bias supply pot output, but given the huge number of variables, especially in the plate current characteristics from tube-to-tube, the bias voltage by itself is almost meaningless). In the real world, I suspect that most Sunn 60 Watters are biased in the +/-40mA (per tube) range at idle (e.g., my stock Solarus w/5AR4 and GE 6550A's gives me the sound I like at around 38mA per side while my later solid state-rectified Sceptre, hotrodded with the 120W power transformer and KT88s likes 44mA. The B+ is 540V and 560V, respectively). But look at how hot Dynaco was running them originally: 70mA idle per tube! (just do the simple math: 1.56V across an 11.2 ohm cathode resistor = 140mA). Starting to push close to max. plate dissipation rating and running the amp at a rather high Class AB operating point. That much idle current really sucks down the B+, especially with the higher impedance power supply resulting from using a tube rectifier.
Kind of a long way of saying (but I think relevant to show all the pieces of the puzzle to properly make the point) that depending upon how hot or cold you like to bias your output tubes, you will see major differences in the B+ voltage you end up with. So don't get too hung up on the voltage in your amp compared to what you read about, as long as it is reasonably consistent w/ your bias settings and everything else checks out and the amp sounds good.
P.S. to MusicFox, my Sentura I and early Solarus, both 40 Watters, each show about 490 plate volts with the output biased at ~38mA per tube.
No matter what you've got, Sunn = Fun!!
